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Constant preheat and thermal runaway errors!  

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PrinterGuy74
(@printerguy74)
New Member
Constant preheat and thermal runaway errors!

So I finished assembling the MK3 yesterday and ran the wizard with checks across the board. I printed the logo and a few test files and all wass good. I started a longer(6hr print) and went to bed. I woke up to a thermal runaway error. 

Since then I have not gotten past the preheat cycle. I've spent the morning trouble shooting with no luck. Here's what Ive done so far:

Check and reseated both thermistor connections on the board.

Firmware flash

Used a haridryer on both the bed and hotend and both registered temperature increases

I've tried heating up the hot end and bed individually and they randomly heat up but never to full temp then a preheat fail. If I try a PLA preheat, and the bed led happens to come on, when the bed hits about 50C and then the led goes off and both the bed and hotend stop heating. Finally reran the wizard and I cant get past the bed and hotend temp checks.

I've run out of ideas. It feels to me like a hardware(einsy/PSU) problem but I'm not sure how to diagnose that. 

Anyone out there got any idea...Cheers!

Postato : 20/12/2019 5:57 pm
Kmac1036
(@kmac1036)
Active Member
RE: Constant preheat and thermal runaway errors!

I guess triple check your thermistor connectors on the control board, make sure they're in the correct spot, not flipped or making poor contact & try the hard reset this user mentions: https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/assembly-finished-startup-errors-z-axis-stiff/#post-179836

I've had this on another bot after flashing firmware which didn't have the heated bed thermistor set. could try the firmware route if all else fails.

Printrbot Play & new i3 MK3s owner.

Postato : 23/12/2019 7:32 pm
PrinterGuy74
(@printerguy74)
New Member
Topic starter answered:
RE: Constant preheat and thermal runaway errors!

Thanks for the reply. I checked all the connections and noticed some weird behaviour that makes me think it may be the hotend thermistor. When the preheat cycle fails and I unplug and re-plug the thermistor wire the red bed led comes on immediately and attempts another preheat. Previously, the light wouldnt come on at all for 5 or 10 minutes. I'll talk to support.

Cheers

Postato : 24/12/2019 6:31 am
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